Bus trace macrocell to make bus information visible that you cannot infer from core trace.

Why Embedded Trace Macrocells?

When it comes to debug or to optimize an embedded system, embedded developers have two main options available to them:

Conventional debug: typically setting breakpoints and/or watch points to halt the processing unit and from there use a debug connection to examine or modify register or memory and single-step to understand how the program works.

While enabling developers to control the execution and debug their code, conventional debug has several disadvantages:

Intrusive: debug halters the behavior of the system

Requirement to stop the processor, for some applications it may not be possible to stop the processor (e.g. hard-disk, automotive, …)

Non real-time: cannot be used to debug software operating real-time.

No performance visibility: cannot observe software performance.

Real-time trace: when the system is running, trace macrocells collect instruction and / or data transfer, compress this information and deliver off-chip in real-time or on-chip for post processing.
Trace is post-merged with source code in development workstation for later analysis.

The CoreSight Embedded trace macrocells enable developers to accelerate their product developments and deliver high quality optimized software by analyzing in real-time how the software operates on the platform.
ETM and PTM main features and benefits are:

Main Feature

Main Benefits

Trace the core at full speed with zero performance overhead

Trace and debug your system executing in real-time

Cycle-accurate trace

Collect vital timing on program execution for performance optimizations and ‘always-in-time’ code verification

CPU Trace Macrocells™ (ETM / PTM)

Embedded Trace Macrocells™ (ETM) and Program Trace Macrocells™ (PTM) provide comprehensive debug and trace facilities for ARM processors. They allow capture of information on the processor both before and after a specific event, while adding no burden to the processor's performance, while the processor runs at full speed.

The ARM CPU trace macrocell family comprises the CoreSight ETM and PTM for Cortex™ processors (A, R and M series) and the ETM11™, ETM9™, ETM7™.

The Embedded Trace Macrocell can be configured in software to capture only select trace information and only after a specific sequence of conditions, see Table 1.

The CoreSight SoC infrastructure enables the compressed trace data to either be captured on-chip using an Embedded Trace Buffer or to be read from the chip by an external trace port analyzer (such the RealView Trace unit) without interrupting, or effecting, the processor. More details on CoreSight SoC components.

CoreSight ETMs & PTM, designed for use both standalone and within a multi-core environment using the features of the CoreSight Design Kits, allow the developer to view simultaneous, correlated trace from multiple, asynchronous cores.

Table 1 - ETM Features

Feature

#

Address Comparators

8

Data Comparators

2

Address Range Comparators

4

16-bit Counters

2

Three-stage Sequencer

1

External Inputs

4

External Outputs

2*

Notes
Areas are from trial synthesis, post layout.
ETM7 (medium) has only one external output.

Embedded Trace Macrocells (ETM)

ETM macrocells provide real-time instruction trace and data trace for the ARM microprocessor. The ETM generates information that trace software tools use to reconstruct the execution of all or part of a program.

Program Trace Macrocell (PTM)

The PTM is a module that performs real-time instruction flow tracing based on the Program Flow Trace (PFT) architecture. The PTM generates information that trace tools use to reconstruct the execution of all or part of a program.

AHB Trace Macrocell (HTM)

The HTM makes bus information visible that you cannot infer from core trace using an ETM:

An understanding of multi-layer bus utilization.

Software debug. For example, visibility of access to memory areas and data accesses.

Bus event detection for trace trigger or filters, and for bus profiling.

The HTM provides address and data trace information about AHB buses. The information from an HTM, used with the debugger, enables easy, accurate debugging on AHB-based embedded systems. The HTM provides extensive resources for event recognition to generate trigger events. The HTM generates trace data for output through the AMBA Trace Bus (ATB). The trace debug function is non-intrusive. HTM can be controlled using an APB (AMBA v3) interface

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